Re: [PATCH v12 1/4] pstore/blk: new support logger for block devices

[liaoweixiong <liaoweixiong@allwinnertech.com>]

hi Dan Carpenter,

On 2019/03/05 15:12, Dan Carpenter wrote:
> Hi liaoweixiong,
> 
> url:    https://github.com/0day-ci/linux/commits/liaoweixiong/pstore-block-new-support-logger-for-block-devices/20190303-142003
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/pstore
> 
> smatch warnings:
> fs/pstore/blkzone.c:180 blkz_zone_write() error: we previously assumed 'zone->buffer' could be null (see line 167)
> 
> # https://github.com/0day-ci/linux/commit/113727d0f1946ad094dbc6531d653a88c7a221bf
> git remote add linux-review https://github.com/0day-ci/linux
> git remote update linux-review
> git checkout 113727d0f1946ad094dbc6531d653a88c7a221bf
> vim +180 fs/pstore/blkzone.c
> 
> 113727d0 liaoweixiong 2019-02-28  153  
> 113727d0 liaoweixiong 2019-02-28  154  static int blkz_zone_write(struct blkz_zone *zone,
> 113727d0 liaoweixiong 2019-02-28  155  		enum blkz_flush_mode flush_mode, const char *buf,
> 113727d0 liaoweixiong 2019-02-28  156  		size_t len, unsigned long off)
> 113727d0 liaoweixiong 2019-02-28  157  {
> 113727d0 liaoweixiong 2019-02-28  158  	struct blkz_info *info = blkz_cxt.bzinfo;
> 113727d0 liaoweixiong 2019-02-28  159  	ssize_t wcnt;
> 113727d0 liaoweixiong 2019-02-28  160  	ssize_t (*writeop)(const char *buf, size_t bytes, loff_t pos);
> 113727d0 liaoweixiong 2019-02-28  161  	size_t wlen;
> 113727d0 liaoweixiong 2019-02-28  162  
> 113727d0 liaoweixiong 2019-02-28  163  	if (off > zone->buffer_size)
> 113727d0 liaoweixiong 2019-02-28  164  		return -EINVAL;
> 113727d0 liaoweixiong 2019-02-28  165  	wlen = min_t(size_t, len, zone->buffer_size - off);
> 113727d0 liaoweixiong 2019-02-28  166  	if (flush_mode != FLUSH_META && flush_mode != FLUSH_NONE) {
> 113727d0 liaoweixiong 2019-02-28 @167  		if (buf && zone->buffer)
>                                                            ^^^^^^^^^^^^
> Check.
> 

zone->buffer should not be checked whether null as it will never be null
here. I will fix it on next version.
zone->buffer was allocated when the zone was initialized (see line 995).
Pstore/blk will not go on if allocates buffer for zone->buffer failed.

> 113727d0 liaoweixiong 2019-02-28  168  			memcpy(zone->buffer->data + off, buf, wlen);
> 113727d0 liaoweixiong 2019-02-28  169  		atomic_set(&zone->buffer->datalen, wlen + off);
> 113727d0 liaoweixiong 2019-02-28  170  	}
> 113727d0 liaoweixiong 2019-02-28  171  
> 113727d0 liaoweixiong 2019-02-28  172  	writeop = is_on_panic() ? info->panic_write : info->write;
> 113727d0 liaoweixiong 2019-02-28  173  	if (!writeop)
> 113727d0 liaoweixiong 2019-02-28  174  		return -EINVAL;
> 113727d0 liaoweixiong 2019-02-28  175  
> 113727d0 liaoweixiong 2019-02-28  176  	switch (flush_mode) {
> 113727d0 liaoweixiong 2019-02-28  177  	case FLUSH_NONE:
> 113727d0 liaoweixiong 2019-02-28  178  		return 0;
> 113727d0 liaoweixiong 2019-02-28  179  	case FLUSH_PART:
> 113727d0 liaoweixiong 2019-02-28 @180  		wcnt = writeop((const char *)zone->buffer->data + off, wlen,
>                                                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Unchecked.
> 
> 113727d0 liaoweixiong 2019-02-28  181  				zone->off + sizeof(*zone->buffer) + off);
>                                                                                     ^^^^^^^^^^^^
> This is weird.  I can't fetch for-next/pstore so I don't know what
> type "buffer" is.  It's vague.  We also have ->buffer_size which seems
> like a more expected way to describe the size.
> 

The type of buffer is struct blkz_buffer (see line 98). struct
blkz_buffer is a header of data, who's member data[0] point to real
data. The codes "sizeof(*zone->buffer)" just to get size of header.
There is a size recorder for blkz_buffer->data on struct blkz_zone. It
is no need to write to block device, that's why it do not live in struct
blkz_buffer.

> 113727d0 liaoweixiong 2019-02-28  182  		if (wcnt != wlen)
> 113727d0 liaoweixiong 2019-02-28  183  			goto set_dirty;
> 113727d0 liaoweixiong 2019-02-28  184  	case FLUSH_META:
> 113727d0 liaoweixiong 2019-02-28  185  		wlen = sizeof(struct blkz_buffer);
> 113727d0 liaoweixiong 2019-02-28  186  		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
> 113727d0 liaoweixiong 2019-02-28  187  		if (wcnt != wlen)
> 113727d0 liaoweixiong 2019-02-28  188  			goto set_dirty;
> 113727d0 liaoweixiong 2019-02-28  189  		break;
> 113727d0 liaoweixiong 2019-02-28  190  	case FLUSH_ALL:
> 113727d0 liaoweixiong 2019-02-28  191  		wlen = buffer_datalen(zone) + sizeof(*zone->buffer);
> 113727d0 liaoweixiong 2019-02-28  192  		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
> 113727d0 liaoweixiong 2019-02-28  193  		if (wcnt != wlen)
> 113727d0 liaoweixiong 2019-02-28  194  			goto set_dirty;
> 113727d0 liaoweixiong 2019-02-28  195  		break;
> 113727d0 liaoweixiong 2019-02-28  196  	}
> 113727d0 liaoweixiong 2019-02-28  197  
> 113727d0 liaoweixiong 2019-02-28  198  	return 0;
> 113727d0 liaoweixiong 2019-02-28  199  set_dirty:
> 113727d0 liaoweixiong 2019-02-28  200  	pr_err("write failed with %zd returned, set dirty\n", wcnt);
> 113727d0 liaoweixiong 2019-02-28  201  	atomic_set(&zone->dirty, true);
> 113727d0 liaoweixiong 2019-02-28  202  	return -EBUSY;
> 113727d0 liaoweixiong 2019-02-28  203  }
> 113727d0 liaoweixiong 2019-02-28  204  
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> 

-- 
liaoweixiong